[Expression of ubiquitin in the spleen and its influence on the dendritic cell immunomodulation function in multiple...

To explore the expression change in ubiquitin (Ub) in the spleen and its significance in multiple organ dysfunction syndrome (MODS) in mice, and to study the effects of ubiquitination of major histocompatibility complex II (MHCII) on the activity and immunomodulation function of splenic dendritic cell (DC).

Two hundred and ten mice were divided into the normal control group (n = 30) and MODS group (n = 180) according to the method of random digital table, and MODS model was replicated by intraperitoneal injection of zymosan. The MODS group mice were further divided evenly into 6, 12, 24, 48-hour and 5-7-day and 10-12-day groups. Ub protein and expression of CD11c⁺DC and MHCII molecule I-A(b) were examined using immunohistochemistry and immunofluorescence methods. Ub mRNA expression in the spleen was measured by real-time quantitative reverse transcription--polymerase chain reaction (RT-PCR).

(1)Immunohistochemistry results showed: the number of Ub positive cells in the spleen increased significantly at 6 hours in MODS group compared with that of the normal control group, and it reached the peak at 24 hours [(16.83 ± 0.38)% vs. (8.60 ± 0.86)%, P < 0.05] and then decreased gradually. At 10-12 days, the number of Ub positive cells decreased significantly compared with that of the normal control group [(4.66 ± 0.34)% vs. (8.60 ± 0.86)%, P < 0.05]. (2)RT-PCR results displayed: compared with normal control group, Ub mRNA expression in spleen increased at 6 hours in MODS group, and it reached the peak at 24 hours (2.17 ± 0.20 vs. 1.00 ± 0.00, P < 0.01). Then, it decreased gradually. At 10-12 days, Ub mRNA decreased significantly as compared with that of normal control group (0.72 ± 0.08 vs. 1.00 ± 0.00, P < 0.05). (3)Immunofluorescence results displayed: compared with normal control group, CD11c⁺DC increased significantly at 6 hours in MODS group and reached the peak at 24 hours [(7.55 ± 0.04)% vs. (2.08 ± 0.13)%, P < 0.05], and then it decreased gradually. At 10-12 days, it was close to that of the normal control group [(2.28 ± 0.06)% vs. (2.08 ± 0.13)%, P>0.05]. Compared with the normal control group, I-A(b) positive cells in the spleen was significantly increased at 6 hours in MODS group [(10.90 ± 1.40)% vs. (5.78 ± 0.47)%, P < 0.01], but it decreased at 24 hours [(3.32 ± 0.91)% vs. (5.78 ± 0.47)%, P < 0.05]. I-A(b) positive cells were restored to the normal level at 48 hours and 5--7 days, and decreased significantly again at 10-12 days [(2.20 ± 0.97)% vs. (5.78 ± 0.47)%, P < 0.05]. The number of Ub positive cells correlated positively to the expression of I-A(b) and the CD11c [r₁ = 0.899, r₂=0.987, both P < 0.05].

Ub might influence the maturation and activation of DC via ubiquitination of the MHCII molecule on DC, thereby influencing the immune response at different stages of MODS. The result might provide a new way to recognize immune response and also a new monitoring index for immune response regulation.